Heat-sensitive recording media are well known in the art which make use of the reaction between a colorless or pale-colored basic dye and a color developing material and give images upon application of heat which brings the color developing material into contact with the basic dye. Such heat-sensitive recording media have the drawback that record images generally have insufficient storage stability and become faded with the lapse of time. Particularly when heat-sensitive recording media are stored under high humidity and/or high temperature conditions, record images may fade away in a relatively short period of time. Improvement in this respect is earnestly desired.
For improving the storage stability of record images, various heat-sensitive recording media containing a storage stability improving agent or agents have been proposed. However, the improvement in storage stability is generally compromised by newly accompanying drawbacks such as reduced whiteness and adhesion of residual substances to the thermal head. Thus, the results are not invariably satisfactory.